Electric power tool

Abstract

An electric power tool may include a three-phase brushless motor configured to drive a tool, a gear reducer provided between the motor and the tool. The gear reducer is configured to selectively change a reduction ratio from the motor to the tool between a first reduction ratio and a second reduction ratio. The electric power tool may further include a motor controller configured to drive the motor with rectangular waves. The motor controller is configured to selectively change a conduction angle of each rectangular wave between at least a first conduction angle and a second conduction angle.

What is claimed is: 
     
       1. An electric power tool comprising:
 a three-phase brushless motor configured to drive a tool; 
 a gear reducer provided between the motor and the tool, the gear reducer being configured to selectively change a reduction ratio from the motor to the tool between a first reduction ratio and a second reduction ratio; and 
 a motor controller configured to drive the motor with rectangular waves, the motor controller being configured to selectively change a conduction angle of each rectangular wave between at least a first conduction angle and a second conduction angle. 
 
     
     
       2. The electric power tool according to  claim 1 , wherein the motor controller is configured to selectively perform a first drive mode in which the conduction angle is maintained at a fixed conduction angle and a second drive mode in which the conduction angle is selectively changed between at least the first conduction angle and the second conduction angle. 
     
     
       3. The electric power tool according to  claim 2 , further comprising:
 at least one manipulation member configured to be manipulated by a user, 
 wherein the motor controller is configured to selectively perform either the first drive mode or the second drive mode in accordance with manipulation applied to the at least one manipulation member. 
 
     
     
       4. The electric power tool according to  claim 3 , wherein
 the at least one manipulation member comprises a first manipulation member for switching between the first drive mode and the second drive mode, and 
 the motor controller is configured to selectively perform either the first drive mode or the second drive mode in accordance with manipulation applied to the first manipulation member. 
 
     
     
       5. The electric power tool according to  claim 3 , wherein
 the at least one manipulation member comprises a second manipulation member for changing the reduction ratio of the gear reducer between the first reduction ratio and the second reduction ratio, and 
 the motor controller is configured to selectively perform either the first drive mode or the second drive mode in accordance with manipulation applied to the second manipulation member. 
 
     
     
       6. The electric power tool according to  claim 5 , wherein
 the second manipulation member is configured to be manipulated between a first position and a second position by the user, 
 when the second manipulation member is manipulated to the first position, the gear reducer sets the reduction ratio at the first reduction ratio and the motor controller selects the first drive mode, and 
 when the second manipulation member is manipulated to the second position, the gear reducer sets the reduction ratio at the second reduction ratio and the motor controller selects the second drive mode. 
 
     
     
       7. The electric power tool according to  claim 6 , wherein the second reduction ratio is smaller than the first reduction ratio. 
     
     
       8. The electric power tool according to  claim 3 , wherein
 the at least one manipulation member comprises a third manipulation member for switching a rotational direction of the tool between a forward direction and a reverse direction, and 
 the motor controller is configured to selectively perform either the first drive mode or the second drive mode in accordance with manipulation applied to the third manipulation member. 
 
     
     
       9. The electric power tool according to  claim 8 , wherein
 the third manipulation member is configured to be manipulated between a third position and a fourth position by the user, 
 when the third manipulation member is manipulated to the third position, the rotational direction of the tool is set to the forward direction and the motor controller selects the second drive mode, and 
 when the third manipulation member is manipulated to the fourth position, the rotational direction of the tool is set to the reverse direction and the motor controller selects the first drive mode. 
 
     
     
       10. The electric power tool according to  claim 3 , wherein
 the at least one manipulation member comprises a second manipulation member configured to be manipulated between a first position and a second position by the user and a third manipulation member configured to be manipulated between a third position and a fourth position by the user, 
 the second manipulation member is configured such that the reduction ratio of the gear reducer is set to the first reduction ratio when the second manipulation member is manipulated to the first position, and such that the reduction ratio of the gear reducer is set to the second reduction ratio when the second manipulation member is manipulated to the second position, 
 the third manipulation member is configured such that a rotational direction of the tool is set to a forward direction when the third manipulation member is manipulated to the third position, and such that the rotational direction of the tool is set to a reverse direction when the third manipulation member is manipulated to the fourth position, and 
 the motor controller is configured to select the second drive mode only when the second manipulation member is manipulated to the second position and the third manipulation member is manipulated to the third position. 
 
     
     
       11. The electric power tool according to  claim 1 , wherein the motor controller is configured to change the conduction angle in accordance with a condition index which varies depending on load applied to the tool. 
     
     
       12. The electric power tool according to  claim 11 , wherein the condition index is at least one index selected from a group consisting of: a current of the motor, a rotational speed of the motor, a temperature of the motor, a voltage of a battery which supplies electric power to the motor, and a temperature of a switching element of the motor controller. 
     
     
       13. The electric power tool according to  claim 11 , wherein the motor controller is configured to store at least one threshold value regarding the condition index and change the conduction angle based on a magnitude relationship between the condition index and the at least one threshold value. 
     
     
       14. The electric power tool according to  claim 13 , wherein
 the at least one threshold value includes a first threshold value and a second threshold value, 
 the motor controller is configured to change the conduction angle to the second conduction angle based on a magnitude relationship between the condition index and the first threshold value when the conduction angle is set to the first conduction angle, and 
 the motor controller is configured to change the conduction angle to the first conduction angle based on a magnitude relationship between the condition index and the second threshold value when the conduction angle is set at the second conduction angle. 
 
     
     
       15. The electric power tool according to  claim 13 , wherein
 the at least one threshold value includes a first threshold value, a second threshold value, a third threshold value and a fourth threshold value, 
 the motor controller is configured to change the conduction angle to the second conduction angle based on a magnitude relationship between the condition index and the first threshold value when the reduction ratio of the gear reducer is set at the first reduction ratio and the conduction angle is set at the first conduction angle, 
 the motor controller is configured to change the conduction angle to the first conduction angle based on a magnitude relationship between the condition index and the second threshold value when the reduction ratio of the gear reducer is set at the first reduction ratio and the conduction angle is set at the second conduction angle, 
 the motor controller is configured to change the conduction angle to the second conduction angle based on a magnitude relationship between the condition index and the third threshold value when the reduction ratio of the gear reducer is set at the second reduction ratio and the conduction angle is set at the first conduction angle, and 
 the motor controller is configured to change the conduction angle to the first conduction angle based on a magnitude relationship between the condition index and the fourth threshold value when the reduction ratio of the gear reducer is set at the second reduction ratio and the conduction angle is set at the second conduction angle. 
 
     
     
       16. The electric power tool according to  claim 1 , further comprising a notifier configured to notify the conduction angle set by the motor controller. 
     
     
       17. The electric power tool according to  claim 1 , further comprising a notifier configured to notify the reduction ratio set by the gear reducer. 
     
     
       18. The electric power tool according to  claim 1 , further comprising a first detector configured to detect the reduction ratio set by the gear reducer. 
     
     
       19. The electric power tool according to  claim 18 , wherein the first detector comprises a non-contact sensor. 
     
     
       20. The electric power tool according to  claim 1 , further comprising:
 a second detector configured to detect a rotational speed of the tool, 
 wherein the motor controller is configured to detect the reduction ratio set by the gear reducer based on a detected value by the second detector.